The present invention relates, in general to a method for enhancing solid materials, and more particularly, to a novel method for enhancing aluminum nitride.
In the past sputtered aluminum nitride films have been utilized in a variety of microelectronics applications. One disadvantage of these prior films is the poor chemical stability of the as-deposited films. As-deposited, the sputtered aluminum nitride films contain a high percentage of dangling chemical bonds, are relatively porous, are less dense than epitaxially-grown single crystal aluminum nitride, and do not have a high degree of preferred crystal orientation. These physical properties make the prior films highly reactive with hot aqueous solutions and other liquid chemicals, leading to hydrolysis, oxidation or dissolution of the aluminum nitride films.
The prior as-deposited films can also readily absorb and react with trace oxygen or moisture in the processing gases at an elevated temperature. Additionally, these films may have poor preferred orientation and a high degree of crystalline defects. Aluminum nitride contaminated with trace amounts of oxygen and having poor preferred orientation can result in poor piezoelectric properties when used in acoustic wave devices.
Treatment of thin films with aqueous solutions or gas mixtures at elevated temperatures are commonly employed in the processing of semiconductor devices. Accordingly, it would be desirable to fabricate an aluminum nitride film that is chemically non-reactive with such solutions and gases.
Additionally, it would be desirable to fabricate aluminum nitride thin films which are particularly suited for piezoelectric devices such as Surface Acoustic Wave (SAW) transducers or resonators.